A = Access (can be free or paid, open or restricted, immediate or delayed)SA = Subscription Access (also called TA: toll access, to include subscription access, licensed access, and pay-to-view)OA = Open Access (immediate, permanent, Gratis or Libre)Gratis OA = toll-free online accessLibre OA = toll-free online access plus certain re-use rightsDA = Delayed Access (free online access after a delay period or embargo)Green OA = OA provided by author self-archivingGold OA = OA provided by the publisher -- sometimes, but not always, for a publication feeGreen DA = free online access provided by the author after a delay (instead of immediately upon publication, which would have been Green OA)Gold DA = free online access provided by the publisher after a delay (instead of immediately upon publication, which would have been Gold OA)

The purpose of Open Access (OA) is to maximize the uptake, usage, applications and impact of research findings by making them accessible to all users online, rather than just to those users who have subscription access (SA).

There are two ways for authors to make access to their published findings free for all: Publish them in a journal that makes the articles free for all online ("Gold OA"). Or publish them in any journal at all, but also self-archive the final, peer-reviewed draft free for all online ("Green OA").

But both the Green and the Gold paths to access can be taken immediately, or only after a delay of months or years.

If subscription access (SA) is not OA but restricted access, because it is restricted to subscribers only, then surely both delayed Green Access and delayed Gold Access are not OA either, because access is restricted during any delay period.

Some journals, for example, impose a 12-month embargo on Green self-archiving. And of those subscription journals where the journal itself makes its articles freely accessible at no extra charge to the author, some journals only do so 12 months after publication or longer.

In many fields, the growth tip for accessing and building upon new findings is within the first year or even earlier. (See the figure from Gentil-Beccot 2009). With delays, potential research progress is slowed and reduced, some of it perhaps even permanently lost.

Hence 50% DA is certainly better than 25% DA -- but until research has 100% OA, there's really not that much to tipple about...

The American Scientist Open Access Forum has been chronicling and often directing the course of progress in providing Open Access to Universities' Peer-Reviewed Research Articles since its inception in the US in 1998 by the American Scientist, published by the Sigma Xi Society.

The Forum is largely for policy-makers at universities, research institutions and research funding agencies worldwide who are interested in institutional Open Acess Provision policy. (It is not a general discussion group for serials, pricing or publishing issues: it is specifically focussed on institutional Open Acess policy.)